The University of Virginia Gene Targeting and Transgenic Facility (GTTF) is a Shared Resource that utilizes advanced transgenic and gene targeting technologies to efficiently produce and preserve genetically engineered mice for cancer model research for UVA Cancer Center investigators. The GTTF's mission is to support transgenic and gene targeting research endeavors, to provide efficient genetic technologies for germline and embryonic stem cell manipulations, and to serve as a resource for design, development and derivation of customized cancer-prone mouse strains. For the past five years, the GTTF has evolved into a unique shared resource that provides a range of integrated services covering five areas: (1) transgenic and knockout/knock-in mouse production, (2) gene targeting, (3) embryo cryopreservation/reconstitution, (4) mouse genetic analysis and (5) training. The GTTF is uniquely positioned to support cancer research. While cancer researchers have successfully studied the molecular and cellular properties of cancer cells propagated in culture, increasingly mouse models of cancer provide a more physiologically relevant opportunity to investigate the interplay of cancer cells, the tumor microenvironment, and the host immune system. Mouse models provide opportunities to study the evolution of cancer progression from first mutations to metastasis, and the unique opportunity to assess the genetic and epigenetic events correlated with acquisition of drug resistance. The overall goal of the GTTF is to provide the support with integrated service and training to make mouse model design, creation and preservation as seamless as possible for the benefit of researchers in the Cancer Center.